This invention relates to oxetane compounds containing cinnamyl functionality.
Oxetanes are highly reactive cyclic ethers that can undergo both cationic and anionic ring opening homopolymerization. Cinnamyl compounds are capable of free radical polymerization.
This invention relates to compounds that contain an oxetane functionality and a cinnamyl functionality. These compounds can be homopolymerizable in reactions in which the oxetane can undergo cationic or anionic ring opening, or polymerizable with compounds such as electron acceptor compounds. The dual functionality allows for dual cure processing, both thermal cure or radiation cure. This capability makes them attractive for use in many applications, such as, adhesives, coatings, encapsulants, and composites.
In one embodiment, the compounds of this invention can be represented by the formula 
in which R is a methyl or ethyl group, X and Y independently are a direct bond, provided both are not direct bonds, or an ether, ester, or carbamate group, and Q is a divalent hydrocarbon. The actual configuration of the Q portion will depend on the configuration of the starting compounds.
The starting cinnamyl compound can be small molecule, for example, cinnamyl alcohol or cinnamyl chloride, or can be an oligomeric or polymeric molecule, prepared by reacting cinnamyl alcohol or cinnamyl chloride with one functionality on a difunctional oligomer or polymer.
Whether the starting cinnamyl compound is a small molecule or an oligomeric or polymeric material, it will contain a cinnamyl functionality represented by the structural formula 
and a second functionality reactive with a second functionality on the starting oxetane compound. For example, the cinnamyl starting materials disclosed above contain halogen or hydroxyl functionality in addition to the cinnamyl functionality.
The starting oxetane compound can be a small molecule or an oligomeric or polymeric molecule, prepared, for example, by reacting one of the small molecule oxetane starting compounds disclosed below with one functionality on a difunctional oligomer or polymer. In either case, it will contain an oxetane functionality represented by the structure 
and a second functionality reactive with the second functionality on the cinnamyl starting compound.
Suitable starting oxetane compounds that are small molecules include, for example,
(a) alcohols, such as, 3-methyl-3-hydroxymethyloxetane, 3-ethyl-3-hydroxymethyloxetane; 
(b) halides, such as, 3-methyl-3-bromomethyloxetane, 3-ethyl-3-bromomethyloxetane, which can be prepared by the reaction of an alcohol from (a) with CBr4 as is known in the art; 
(c) alkyl halides, such as, 3-methyl-3-alkylbromomethyloxetane, 3-ethyl-3-alkylbromomethyloxetane, which can be prepared from the reaction of an alkyl dibromide compound with an oxetane alcohol from (a) as is known in the art; 
and (d) tosylates, such as, 3-methyl-3-tosylmethyloxetane, 3-ethyl-3-tosylmethyl-oxetane, which can be prepared from p-toluenesulfonyl chloride: 
When a longer chain and higher molecular weight compound containing cinnamyl and oxetane is desired, either the starting cinnamyl compound or the starting oxetane compound, or both, may be reacted with a difunctional oligomeric or polymeric material. The second functionality on this oligomeric or polymeric material must be reactive with the oxetane starting compound if the first reaction was between the cinnamyl starting compound and the difunctional oligomeric or polymeric material, and with the cinnamyl starting compound if the first reaction was between the oxetane starting compound and the difunctional oligomeric or polymeric material. Examples of suitable and commercially available oligomers and polymers include dimer diol and poly(butadiene) with terminal hydroxyl functionality.
In the case in which both the oxetane and cinnamyl starting compounds are oligomeric or polymeric, Q may also contain a functionality, for example, an ether, ester, carbamate, or urea functionality, resulting from the reaction of the two oligomeric or polymeric starting materials.
In general, the inventive compounds containing oxetane and cinnamyl functionality are prepared by reacting together a starting compound containing oxetane functionality and a second functionality and a starting compound containing cinnamyl functionality and a second functionality reactive with the second functionality on the oxetane compound. Typical reaction schemes include well known addition, substitution, and condensation reactions.
In a further embodiment, the compounds of this invention include polymeric compounds that contain more than one oxetane and more than one cinnamyl functionality. Such compounds are prepared from a polymeric starting compound from which depend functionalities that are reactive with the starting oxetane compound and the starting cinnamyl compound.
The polymeric compound will have the structure 
in which polymer represents a polymeric backbone from which depend the oxetane and cinnamyl functionalities, m and n are integers that will vary with the level of oxetane and cinnamyl functionality added by the practitioner and typically each will be from 2 to 500, R is methyl or ethyl, and W and Z are independently an ether, ester, or carbamate group (formed through the reaction of a pendant functionality on the polymer and a corresponding reactive functionality on the starting oxetane compound or starting cinnamyl compound).
The pendant functionalities on the polymer may be connected to the polymeric backbone by a hydrocarbon, for example, one having one to twenty carbons, that itself is dependent from the polymeric backbone. For purposes of this specification, those dependent moieties will be deemed to be part of the polymeric backbone.
An example of a commercially available and suitable polymeric backbone is poly(butadiene) having pendant hydroxyl groups. The pendant hydroxyl groups can be reacted with the oxetane starting compound containing the tosyl leaving group and with cinnamyl chloride. In this case, the linking groups W and Z will be an ether functionality.
As a further example, a poly(butadiene) having pendant carboxylic acid functionality can react with the hydroxyl functionality on either of the hydroxyl oxetane starting materials and with the hydroxyl functionality on cinnamyl alcohol. In this case, the W and Z groups will be an ester functionality.
Polymeric starting material can be purchased commercially, for example, there are available acrylonitrile-butadiene rubbers from Zeon Chemicals and styrene-acrylic copolymers from Johnson Polymer. The pendant functionalities from these polymers are hydroxyl or carboxylic acid functionality.
Other starting polymeric materials can be synthesized from acrylic and/or vinyl monomers using standard polymerization techniques known to those skilled in the art. Suitable acrylic monomers include xcex1,xcex2-unsaturated mono and dicarboxylic acids having three to five carbon atoms and acrylate ester monomers (alkyl esters of acrylic and methacrylic acid in which the alkyl groups contain one to fourteen carbon atoms).
Examples are methyl acryate, methyl methacrylate, n-octyl acrylate, n-nonyl methacrylate, and their corresponding branched isomers, such as, 2-ethylhexyl acrylate. Suitable vinyl monomers include vinyl esters, vinyl ethers, vinyl halides, vinylidene halides, and nitriles of ethylenically unsaturated hydrocarbons. Examples are vinyl acetate, acrylamide, 1-octyl acrylamide, acrylic acid, vinyl ethyl ether, vinyl chloride, vinylidene chloride, acrylonitrile, maleic anhydride, and styrene.
Other polymeric starting materials can be prepared from conjugated diene and/or vinyl monomers using standard polymerization techniques known to those skilled in the art. Suitable conjugated diene monomers include butadiene-1,3,2-chlorobutadiene-1,3, isoprene, piperylene and conjugated hexadienes. Suitable vinyl monomers include styrene, xcex1-methylstyrene, divinylbenzene, vinyl chloride, vinyl acetate, vinylidene chloride, methyl methacrylate, ethyl acrylate, vinylpyridine, acrylonitrile, methacrylonitrile, methacrylic acid, itaconic acid and acrylic acid.
Those skilled in the art have sufficient expertise to choose the appropriate combination of those monomers and subsequent reactions to be able to add pendant functionality, for example, hydroxyl and carboxyl functionality, for adding the oxetane and cinnamyl functionalities as disclosed in this specification.